Do I need the red line in this plot? If not, how can I get rid of it?

How do I know the values of the Engine Size of 3, 3.5, 4, 4.5, and 5?

###### STEP 4 ######

# (I) Display a residual plot of the simple regression model made above # Set up the plot with a black background and customize colors par(bg = "black", col.axis = "white", col.lab = "blue", col.main = "blue", col.sub = "blue")

# Plot residuals vs. fitted values with customized colors and styles plot(linear_model, which = 1, col = "blue", pch = 19, main = "Residuals vs. Fitted", col.main = "blue", col.lab = "blue", col.axis = "white", grid(col = "white"))

# Add a regression line with a thicker line width and color is white abline(lm(residuals(linear_model) ~ fitted(linear_model)), col = "white", lwd = 2)

# (II) Use the regression equation to find predicted values of MPG.city # for the following values of EngineSize (liters of displacement):

new_data

# Predict MPG.city using the linear regression model predicted_values

# Display the predicted values predicted_values

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